Method for the concentration of acetic acid



Patented eb. 28, 1928.

UNITED STATES PATENT OFFICE.

JACQUES DUCLAUX, 01 PARIS, FRANCE, ASSIGNOB '10 FABRIQUE 801E v.LIBIIEL FICIE LE .DE TUBIZE, SOCIETE ANONYME, OF BRUSSELS, BELGIUM.

METHOD FOR THE CONCENTRATION OF ACETIG ACID.

No Drawing. Application filed larch 31,-1924,

This invention relates to an improved .Acetic acid and water can be separatedfrom each other by rectifying operations Such operations however as it. is known, have not the same efiioiency which they possess in other cases, as for instance in the separation of alcohol from water. The ordinary rectifiers which are generally industrially used cannot secure a complete separation from acetic acid and water and cannot bring all of the acid to the glacial state.

According to thisinvention, this result is secured by adding to the mixture or aqueous solution of acetic. acid, acetone oil having a suitable boiling point.

The acetone oils which are obtained as residual products, in the rectificationof ordinary acetone, contain agreat number of elements, the boiling points of whichvary from 80 to above 200 C. Moreparticularly they-contain elements the boiling point of which is about 100 C.such as d1-ethyl-- ketone, methyl-propyl and methyl-isopro- 85 pyl-ketone.

When a mixture of water, acetic acid,,and such ketones is distilled, the latter are first distilled at the beginning of the operation in such a manner that the said acid becomes graduall more and more concentrated in the resi ue. If the proportions are exactly calculated, there remains only in the distilling apparatus acetic anhydride after all of 'the water has been expelled. If, on

the contrary, the proportions are not exactly calculated, as is generally the case in practice, there remains finally acetic acid and the ketones which can be separated by a rectifying operation. The onl condition to observe in order that the sai rectlfying o eration may be possible, is that a sufliclent difference must exist between the boiling temperature of the acetic acid (117 C. an that of the ketone which is employe It is for this reason that the use of products Serial no. 703362, and in Germany April 4, 1923.

Thc'ketones, which are here referred to,

have only a slight solubility in water. The vapors which are distilled, ive'whenthey are condensed, a liquid WlllCfi separates into two layers, the lower layer of. which is-water. The upper layer is formed by the 'lretone which may be returned into the dis- -t1ll1ng apparatus tocontinue the same cycle. Under these conditions, the quantity of ketone which is necessary for the operation is only that which'is always circulating and.

which may be very small.

The dehydration of the above described method may be'carried out in acontinuous manner. As an example in arectifyrng apparatus, one of the intermediary plates, which will" be conveniently choosen in practice, will be fed simultaneously with the liquid which is to be con-- acetic acid by the centrated, and with the ketone in such qu'ant1t1es that the ketone and the water will be exactly in the proportions in which they are passing when the are distillated together. If these conditions are observed, the lower plates of the column of the rectifying appiaratus will only eollect anhydrous acetic The constitutents of the acetone oils, the use of which has just been described, may

be employed either in, a pure state or in the form of mixtures. These products do not act chemically one upon another, but the process is based upon the following physi-zcal roperties of these constituents.

T ey form with water,'a system having a boiling point which is lower than the boiling oint of the constituents.

T eir boiling point is sulficiently high and their molecular weight sufiiciently low, so that the vapor which is produced by the system will contain 'a considerable proportion of water vapor; the proportion of water and other substance being determined b the physical constants thereof in the We] known fashionof constant boiling mixtures. Further, the said constituents do not form with acetic acid a system, the boiling point of which is lower than. either ofthe boiling points of the said constituents. .Thus, a mix- 7 during the distillation ture of acetic acid and acetone oils (boiling at 100 C.) has a boili point which varies om 100 C. to 117 (1., but is never lower than 100, while a mixture of acetic acid and acetone oil (boiling at 130 C.) has a boiling point which varies during the distillation from 117 C. to 130 .C., but is never lower than 117 C.

In the first easeit is the oil which passes over first and in the second case it is the acid, but in neither case is the boiling point lower than that of the two constituent/s which is the more volatile. The boiling point of these constituents is, in consequence, sufliciently different from the boiling point of acetic acid so that the separation can be effected by distillation and they are,not. decomposed under the conditions of operation.

Other constituents may be substituted for acetone oils; it is only necessary for this object. that the constituent which is used, possesses the properties which have been enumerated hereabove; but any constituent which does not comply with these properties.

may be excluded.

What I claim is:

1. The method of concentrating acetic acid in water solution which comprlses mixing with the solution a substance, substantially insoluble in water, which forms a constant boiling mixture sufi'iciently different from the boiling point of acetic acid to permit of fractionation with water but not with acetic acid, and subjectin the mixture tofractional distillation, w ereby the constant boiling mixture of water and other substance is removed and substantially anhydrous acetic acid remains behind. I

2. The method of concentrating acetic acid in water solution which comprises mixing a water insoluble acetone oil therewith of a constitution which is water insoluble, but which forms a constant low boiling mixture with water but not with acetic acid sufiicient-ly different from the boiling point acetic acid, having a boiling'point lower than the boiling point of acetic acid, heating the mixture to the constant boiling point of the mixture, removing all the vapor of the co'nstant'boiling mixture, heating the residue to the boiling point of the ketone, andremoving the .vapor of the ketone, leaving substalllitially pure anhydrous acetic acid in the sti 4:- The method of concentrating solutions of acetic acid, the said method consisting in adding, to the solution, acetone-oils having a boiling point of about 100-130 G. and then subjecting the mixture -to a rectifying operation, whereby the acetic acid becomes concentrated and is obtained as concentrated acetic acid.

5. The method of concentrating aqueous solutions of acetic acid, the said method consisting in adding to the solution, acetone oils having a boiling point of'about 10(130 C. and then subjecting the mixture to -U continuous rectifying operation, whereby concentrated acetic acid is obtained. v

In testimony whereof I have aflixed my 1 signature.

i JACQUES DUGLAUX. 

